Self-propelled device for milling road surfaces

ABSTRACT

The invention relates to a self-propelled device for milling road surfaces with a vertically adjustable chassis, which carries a steerable travelling mechanism with at least one steering wheel and a rear pair of wheels with individual wheel drives and a drive unit for them and for driving a milling unit which is coupled to the drive unit and comprises a milling roller which extends transversely to the travelling direction, has a width smaller than the width of the device and is arranged off-centre with respect to the device, the traction of at least one wheel being modified in a way corresponding to at least partial compensation for the moment acting about the vertical axis of the device during milling.

FIELD OF THE INVENTION

The invention relates to a self-propelled device for milling road surfaces.

BACKGROUND OF THE INVENTION

In the case of small devices for milling road surfaces, known as compact millers, the milling unit is usually arranged flush with one side of the device and at a distance from the other side of the device, since it has a relatively small width in comparison with the width of the device, corresponding for example to half the width of the device. Accordingly, the force applied to the device is offset considerably from the middle. This offset creates a moment about the vertical axis of the device. This has the effect that the device has the tendency to be forced out of line during the milling operation. This can be compensated by constantly steering against it. However, this leads to a corresponding operating effort and wearing of the tyres.

It is also known to alleviate this problem by providing a swinging-out rear wheel on the side on which the milling unit is arranged flush with the side of the device, with a relatively large swing-out lever, so that as a result the milling unit is located more centrally between the rear wheels when the rear wheel is swung out. Apart from the fact that this leads to a corresponding width of the device, it is not always possible to work with the rear wheel swung out. If milling next to curbstones is intended, this is only possible with the rear wheel swung in, so that then there is still the problem that the device has the tendency to be forced out of line.

SUMMARY OF THE INVENTION

An object of the invention is to provide a device for milling road surfaces with which the tendency of the device to be forced out of line during the milling operation is at least significantly reduced or eliminated in a simple way.

The invention therefore relates to a self-propelled device for milling road surfaces with a vertically adjustable chassis which carries a steerable travelling mechanism with a front and a rear pair of wheels with individual wheel drives and a drive unit for them and for driving a milling unit which is coupled to the drive unit and comprises a milling roller and a milling gear mechanism for it, the milling roller extending transversely to the travelling direction, having a width smaller than the width of the device and being arranged off-centre with respect to the device. In such a device, the traction of at least one wheel is modified in a way corresponding to at least partial compensation for the moment acting about the vertical axis of the device during milling. This consequently allows a distribution of the tractive forces on the individual wheels to be prescribed, to be precise in such a way that the moment produced during the milling operation about the vertical axis of the machine is at least partly compensated and the straight-running of the device is correspondingly improved, even under high milling loads.

In particular, a very simple solution is obtained if at least one of the individual wheel drives has hydraulic axial piston motors connected in parallel, an adjusting device for the traction of the associated wheel, with which the distribution of the tractive forces is influenced in a way corresponding to the at least partial compensation of the moment acting about the vertical axis of the device during milling.

However, it is also possible that at least one individual wheel drive on one side of the device has a gear mechanism with a transmission which is different from the transmissions of gear mechanisms of at least two individual wheel drives of wheels on the other side of the device for at least partial compensation of the moment acting about the vertical axis of the device during milling, or that at least one wheel diameter on one side of the device is different from the wheel diameters of wheels on the other side of the device for at least partial compensation of the moment acting about the vertical axis of the device during milling. However, in these cases the different traction of the wheels is retained during the transporting operation of the device, so that straight-running is adversely affected during the latter. Since the transporting distances to be covered by the device are small, however, this is of minor significance.

Further objects, advantages and embodiments of the invention may be taken from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained below with respect to an embodiment shown in the attached drawings.

FIG. 1 schematically shows a self-propelled device for milling road surfaces in plan view.

FIG. 2 schematically shows the drive system of the device from FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The self-propelled device for milling road surfaces that is represented in the drawings comprises a vertically adjustable chassis 1, which has a steerable travelling mechanism with a front and a rear pair of wheels 2 and receives a drive unit 3, for instance a diesel engine, which drives a pump 4 for hydraulic oil, for instance an axial piston pump. Also coupled to the drive unit 3 is a milling unit 5, which comprises a milling roller 7, which extends transversely to the travelling direction, is provided with milling cutters 6, has a width smaller than the width of the device and is arranged off-centre with respect to the device, in this case flush with the right side of the device.

The device represented comprises a swinging-out, right rear wheel 2, so that, when the rear wheel 2 is swung out, the axis of the rear wheels 2 and the axis of the milling roller 7 lie virtually in a vertical plane. During the transporting operation and during flush milling, for instance along the edge of curbstones or the like, the right rear wheel 2 is swung in, since in the latter case it cannot otherwise run on the road surface.

During the milling operation, the device is moved on the road surface with the overall traction exerted by the wheels 2—arrow 8, the milling roller 7 rotating counter to the travelling direction. As a result of the off-centre arrangement of the milling roller 7, there is a corresponding off-centre application of force to the device—arrow 9, which has the effect that a moment about the vertical axis 10 (running perpendicularly to the plane of the paper of FIG. 1) of the device—arrow 11—substantially corresponding to the distance d between the centre longitudinal plane 12 of the device and the central radial plane 13 of the milling roller 7 is obtained (the not quite uniform mass distribution of the device generally being of minor significance), this moment attempting to force the device out of line.

As represented in FIG. 2, the pump 4 supplies individual wheel drives 14, here axial piston motors, that are connected in parallel with one another with hydraulic oil of equal pressure. The individual wheel drives 14 are respectively provided with an adjusting device 15, for instance a hydraulically or electrically actuated valve, in order to modify the volume of the axial piston motors by adjusting their swash plate. This takes place for example by means of a control 16, which has an adjustable throttle control lever 17.

If the milling unit 5 is then switched on, for instance by means of a switch 18, at same time at least one individual wheel drive 14 is adjusted in a way corresponding to at least partial compensation of the moment acting about the vertical axis 10 of the device during milling, for instance in that the volume of at least one of the axial piston motors is correspondingly modified by means of the associated adjusting device 15.

Expediently, the traction is to be reduced here on that side which is away from the milling unit 5, in the exemplary embodiment represented the left side, at at least one wheel 2, preferably at both wheels 2, for instance in that the volume of the associated axial piston motors is reduced.

However, it may be envisaged additionally or instead to increase the traction on the side near the milling unit 5.

If appropriate, instead of a pair of driveable front wheels 2, the device may also have only a single steerable front wheel 2, which is not necessarily provided with an individual drive.

While the invention has been shown and described with reference to preferred embodiments, it should be apparent to one of ordinary skill in the art that many changes and modifications may be made without departing from the spirit and scope of the invention as defined in the claims. 

1. A self-propelled device for milling road surfaces, comprising: a vertically adjustable chassis, which carries a steerable travelling mechanism with at least one steering wheel and a rear pair of wheels; a drive unit for driving individual wheel drives for the wheels; and a milling unit which is driveably coupled to the drive unit and comprising a milling roller which extends transversely to the travelling direction of the device, the milling roller having a width smaller than the width of the device and is arranged off-centre with respect to the device; wherein the traction of at least one wheel is modified in a way corresponding to at least partial compensation for the moment acting about the vertical axis of the device during milling.
 2. The device according to claim 1, wherein the traction of a rear wheel is modified in a way corresponding to at least partial compensation of the moment acting about the vertical axis of the device during milling.
 3. The device according to claim 1, wherein the traction of a front wheel is modified in a way corresponding to at least partial compensation of the moment acting about the vertical axis of the device during milling.
 4. The device according to claim 1, wherein at least one individual wheel drive has an adjusting device for the traction of the associated wheel for the at least partial compensation of the moment acting about the vertical axis of the device during milling.
 5. The device according to claim 4, wherein the individual wheel drives are hydraulic axial piston motors connected in parallel, at least one of which has an adjusting device for the traction of the associated wheel.
 6. The device according to claim 5, wherein the adjusting device comprises a hydraulically or electrically actuated valve.
 7. The device according to claim 1, wherein on one side of the device at least one individual wheel drive has a gear mechanism with a transmission which is different from the transmissions of gear mechanisms of at least two individual wheel drives of wheels on the other side of the device for at least partial compensation of the moment acting about the vertical axis of the device during milling.
 8. The device according to claim 1, wherein on one side of the device at least one wheel diameter is different from the wheel diameters of wheels on the other side of the device for at least partial compensation of the moment acting about the vertical axis of the device during milling. 